add virtuals to optimize composing colorfilters

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 0a4a693ab0ce71e0272bbf251e548a734b1c774f..fdf6de7b76daf755f2fea5d49c87a753374e3cb7 100755
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -15,61 +15,6 @@
 #include "SkTableColorFilter.h"
 #include "SkWriteBuffer.h"
 
-namespace {
-
-void mult_color_matrix(SkScalar a[20], SkScalar b[20], SkScalar out[20]) {
-    for (int j = 0; j < 4; ++j) {
-        for (int i = 0; i < 5; ++i) {
-            out[i+j*5] = 4 == i ? a[4+j*5] : 0;
-            for (int k = 0; k < 4; ++k)
-                out[i+j*5] += a[k+j*5] * b[i+k*5];
-        }
-    }
-}
-
-// Combines the two lookup tables so that making a lookup using OUT has
-// the same effect as making a lookup through B then A.
-void combine_color_tables(const uint8_t a[4 * 256],
-                          const uint8_t b[4 * 256],
-                          uint8_t out[4 * 256]) {
-    for (int i = 0; i < 4; i++) {
-        for (int j = 0; j < 256; j++) {
-            out[i * 256 + j] = a[i * 256 + b[i * 256 + j]];
-        }
-    }
-}
-
-// To detect if we need to apply clamping after applying a matrix, we check if
-// any output component might go outside of [0, 255] for any combination of
-// input components in [0..255].
-// Each output component is an affine transformation of the input component, so
-// the minimum and maximum values are for any combination of minimum or maximum
-// values of input components (i.e. 0 or 255).
-// E.g. if R' = x*R + y*G + z*B + w*A + t
-// Then the maximum value will be for R=255 if x>0 or R=0 if x<0, and the
-// minimum value will be for R=0 if x>0 or R=255 if x<0.
-// Same goes for all components.
-bool component_needs_clamping(SkScalar row[5]) {
-    SkScalar maxValue = row[4] / 255;
-    SkScalar minValue = row[4] / 255;
-    for (int i = 0; i < 4; ++i) {
-        if (row[i] > 0)
-            maxValue += row[i];
-        else
-            minValue += row[i];
-    }
-    return (maxValue > 1) || (minValue < 0);
-}
-
-bool matrix_needs_clamping(SkScalar matrix[20]) {
-    return component_needs_clamping(matrix)
-        || component_needs_clamping(matrix+5)
-        || component_needs_clamping(matrix+10)
-        || component_needs_clamping(matrix+15);
-}
-
-};
-
 SkColorFilterImageFilter* SkColorFilterImageFilter::Create(SkColorFilter* cf,
         SkImageFilter* input, const CropRect* cropRect, uint32_t uniqueID) {
     if (NULL == cf) {
@@ -77,35 +22,10 @@ SkColorFilterImageFilter* SkColorFilterImageFilter::Create(SkColorFilter* cf,
     }
 
     SkColorFilter* inputColorFilter;
-    if (input && input->asColorFilter(&inputColorFilter) && inputColorFilter) {
+    if (input && input->asColorFilter(&inputColorFilter)) {
         SkAutoUnref autoUnref(inputColorFilter);
-
-        // Try to collapse two consecutive matrix filters
-        SkScalar colorMatrix[20], inputMatrix[20];
-        if (cf->asColorMatrix(colorMatrix) && inputColorFilter->asColorMatrix(inputMatrix)
-                                           && !matrix_needs_clamping(inputMatrix)) {
-            SkScalar combinedMatrix[20];
-            mult_color_matrix(colorMatrix, inputMatrix, combinedMatrix);
-            SkAutoTUnref<SkColorFilter> newCF(SkColorMatrixFilter::Create(combinedMatrix));
-            return SkNEW_ARGS(SkColorFilterImageFilter, (newCF, input->getInput(0), cropRect, 0));
-        }
-
-        // Try to collapse two consecutive table filters
-        SkBitmap colorTable, inputTable;
-        if (cf->asComponentTable(&colorTable) && inputColorFilter->asComponentTable(&inputTable)) {
-            uint8_t combinedTable[4 * 256];
-            SkAutoLockPixels colorLock(colorTable);
-            SkAutoLockPixels inputLock(inputTable);
-
-            combine_color_tables(colorTable.getAddr8(0, 0), inputTable.getAddr8(0, 0),
-                                 combinedTable);
-            SkAutoTUnref<SkColorFilter> newCF(SkTableColorFilter::CreateARGB(
-                        &combinedTable[256 * 0],
-                        &combinedTable[256 * 1],
-                        &combinedTable[256 * 2],
-                        &combinedTable[256 * 3])
-            );
-
+        SkAutoTUnref<SkColorFilter> newCF(cf->newComposed(inputColorFilter));
+        if (newCF) {
             return SkNEW_ARGS(SkColorFilterImageFilter, (newCF, input->getInput(0), cropRect, 0));
         }
     }